Lubricating oil containing silica gel treated bright stock



United StatesPatent it'll 2 991 245 LUBRICATING OIL EODITAINING SILICA GEL TREATED BRIGHT STOCK Harry M. Hartzband, Westfield, and Edwin C. Kruse,

Chatham, N.J., assignors to 'Esso Research and Engineering Company, a corporation of Delaware No Drawing. Filed =Apr. 4, 1957, Ser. No. 650,573 3 Claims. (Cl. 25232.7)

This invention is concerned with an improved lubricating composition. This invention more particularly relates to an improved distillate mineral based automotive lubricating oil composition containing as an additive a silica gel treated bright stock that has the property of reducing or eliminating intake valve underside deposits, while not contributing to the octane requirement increase (O.R.I.) of the engine.

In brief compass, this invention proposes a lubricating oil base stock composition having a viscosity in the range of 50 to 75 SSU at 210 F. and a viscosity index (V.I.) above 120, which comprises a volatile virgin light neutral base stock having an end boiling point below 600 F. at a pressure of 10 mm. Hg absolute, and 3 to 25 wt. percent of a silica gel treated virgin bright stock essentially free from non-hydrocarbons, having a single ring aromatic content below 5 wt. percent and containing essentially no condensed ring aromatics, and having the property of reducing intake valve underside deposits while not contributing to octane requirement increase when used in an internal combustion engine.

Recent advances in automotive engine designs have required marked improvements in lubricants to solve the lubricating problems created by the new designs. Recently, tailor-made lubricating oil compositions have appeared on the market, and these contain select base stocks which are modified by additives to impart desired properties such as high viscosity index (V.I.), detergency, resistance to valve train wear, oxidation stability, low pour point, etc.

It has been recognized that the heavy ends of a base stock tend to form resin-like deposits in internal combustion engine cylinders, which decrease the efiective volume of the cylinder and raise the operating temperature. These deposits have been found to cause an appreciable (-20%) increase in the engine octane requirement, which is highly undesirable. This problem has been solved by using in a lubricating oil composition a light or relatively volatile neutral base stock having an end boiling point below about 600 F. at 10 mm. Hg absolute. By using such a volatile base stock, no deposits are formed in the cylinders and the O.R.I. of the engine is negligible or very moderate.

It has since been discovered, however, that when such light base stocks are used, appreciable deposits of a hard carbonaceous nature are formed on the undersides of the intake valves. The accumulation of these deposits under high mileage can cause severe engine operating difficulties. It appears that these deposits are permitted to form when using a volatile base stock because there are no materials in the oil composition that serve as a solvent or flushing agent to carry the deposit precursors from the valve underside into the engine where they are burned. While it has been realized that the use of bright stocks, i.e., deasphalted residual oils having a viscosity over 100 SSU at 210 F., or other high boiling materials, would supply the necessary solvency or flushing action to remove the deposit precursors, none have been known that would not contribute appreciably to engine O.R.I.

The present invention is directed to this particular problem and proposes a specific solution therefor. This invention is based on the surprising discovery that by select silica gel treatment of a deasphalted, solvent extracted, virgin residual oil or bright stock, a lubricating oil additive is obtained that: (l) overcomes this problem of intake valve underside deposits to a greater degree than conventional bright stocks and (2) does not contribute to O.R.I. Other methods of highly refining bright stocks, such as acid treatment, extensive solvent treatment, or aluminum chloride contacting, do not yield equivalent materials. The reason why silica gel treatment results in such an excellent bright stock is not clearly understood at this time. It is postulated that the silica gel is extremely selective to the removal of aromatics and nonhydrocarbons, both of which contribute to instability. Further, the remaining hydrocarbons have better solvency for the deposits than the original feed, indicating that the treatment leaves some materials in the bright stock in the proper amount, i.e., not too much or too little, that exhibit the desired solvency action in a lubricating oil composition.

It has further been found that the silica gel treated virgin bright stocks of this invention are particularly effective in lubricants containing polymeric V.I. improvers, particularly when used in combination with detergent inhibitors. From available data, it appears that the valve intake deposits are greatly aggravated or increased as the result of a reaction between the V.I. improving and detergent inhibiting components of an oil, particularly when a volatile base stock is used. Silica gel treated bright stocks formed and used in the manner proposed by this invention satisfactorily overcome this problem also.

Another advantage of this invention is that when the silica gel treated virgin bright stock is incorporated into a lubricant based upon a volatile base stock, a substantial savings in cost is realized because a lesser amount of V.I. improver is necessary. The bright stock so contributes to the overall composition that an appreciable amount of V.I. improver can be left out.

The silica geltreated bright stock of this invention can be obtained from any convenient crude source. It is much preferred to use as a starting material paraflinic crudes such as North Louisiana and Panhandle. With crudes other than paraflinic crudes, the treating steps described below result in a substantial loss in yield.

The crude is first treated by simple vacuum distillation to obtain a residual fraction boiling above 950' F. The residual fraction is then at least deasphalted and dewaxed before the silica gel treatment. It is much preferred, however, to also solvent extract the residual fraction before the dewaxing treatment. In some instances the dewaxing step can occur after silica gel treatment, but it is much preferred to carry this out before silica gel treatment and after the deasphalting and solvent extraction steps. I

The residual fraction obtained by vacuum distillation is first treated by deasphalting. Any conventional means of deasphalting canbe used. It is preferred to treat the residual fraction with light paraffins such as propane and butane, or mixtures thereof, at temperatures in the range of to 160 F. and at solvent/oil ratios in the range of 400% to 1200%. The residual fraction is treated to obtain a material having a viscosity at 210 F. in the range of 200 to 250 SSU and a Conradson carbon content of less than 1 wt. percent. For the preferred paraffinic residual fractions, the yields are in the range of 40 to 70 wt. percent.

In a preferred embodiment, the deasphalted fraction is then subjected to solvent extraction employing any conventional solvent such as phenol, furfural, sulfur dioxide, ammonia, nitrobenzene, etc. The extent of the solvent extraction is such as to obtain a material having a V.I. above 100, which reflects the reduction in aromatic content, and a viscosity in the range of 100 to SSU Patented July 4, 1961 at 210 F. The yields are in the range of 50 to 80 wt. percent, based on feed to the extraction step.

In the dewaxing step, the deasphalted residual fraction, which is also preferably solvent extracted as indicated above, is treated to remove the parafiins and to lower its pour point to at least below +30 F. The yield obtained depends upon the wax content of the fraction and is usually in the range of 70 to 90% for paraflinic type residual oils. Conventional dewaxing techniques can be used, solvent dewaxing being preferred. In this method, the residual fraction is contacted with about 2 to 4 parts per volume with a solvent such as propane or methylethylketone. The mixture is then heated to assure solution of the wax, and is then chilled to about 25 to -10 F. to obtain crystallization. The mixture is then filtered or centrifuged to remove the wax.

The bright stock so obtained by the deasphalting and dewaxing steps may then be further treated as desired, such as by decolorizing, as by clay contacting, although this is not usually necessary because the silica gel treatment accomplishes about the same results.

The bright stock is then treated specifically with silica gel to obtain the desired material to add to lubricating compositions. As discussed later (Table VII), other methods of highly refining residual fractions do not give equivalent results. The silica gel treatment is well known in the art and is carried out in a conventional manner by percolating the bright stock, preferably in solution with a solvent such as heptane, through a column of silica gel. A preferred silica gel is the standard commercial 28/200 mesh manufactured by the Davison Chemical Company. It is preferred to contact the bright stock with 300 to 1600 wt. percent of the silica gel at a temperature in the range of 50 to 100 F. The silica gel can be periodically regenerated as desired by standard solvent elutriation, as for example with acetone, benzene, Cellosolve, or mixtures thereof. The silicia gel treatment is sufficient to reduce the concentration of single ring aromatics to below 5 wt. percent and to reduce the condensed ring aromatics to essentially negligible proportions, i.e., less than 0.01 wt. percent. By single ring aromatics are meant compounds containing a single benzene nucleus, and by condensed ring aromatics are meant compounds such as naphthalene anthracene and derivatives thereof, both as determined by spectrographic analysis.

The following Table I gives the inspections of the final silica gel treated virgin bright stock that must be met in order to obtain a suitable lubricating oil additive as proposed by this invention.

TABLE I Viscosity at 210 F., SSU 70 to 150. Viscosity index 100 to 120. Conradson carbon, wt. percent Below 0.1.

Single ring aromatics, wt. percent--. Below 5. Condensed ring aromatics, wt. percent Nil. Pour point, F Below +30. Gravity, API 27 to 32. Tag. Robinson color Above 15. Nitrogen, wt. percent Nil. Sulfur, wt. percent to .05. Initial boiling point Above 850 F. R.I. (resinification index) Below 16 mg./ gr.

and Pennsylvania crude, that has a good viscosity characteristic. The base stocks are distillates that have been refined by conventional procedures including solvent extraction as above described to remove the bulk of the relatively more aromatic, carbon forming, sulfur, etc. constituents. Besides solvent extraction, other conventional treatments such as acid contacting, alkali treatment, contacting with a solid absorbent, clay treatment, hydrogenation, desulfurization such as hydrofining, dewaxing, catalytic cracking and the like can be used. It is much preferred that the final product have a resinification index (R.I.) below about 10 mg./5 gr. as defined below. This means that usually a combination of refining techniques must be used in order to produce a suitable volatile base stock. While it is preferred that the base stock be a virgin stock, other base stocks such as synthetic oils, i.e., di-Z- ethyl-hexyl-sebacate or catalytically cracked materials, e.g., cycle stocks, can be used.

The volatile base stocks used in this invention meet the inspections given in Table II.

TABLE II R1. (resinification index) Below 10 mg./5 gr.

The volatile base stock usually comprises 75 to wt. percent of the final composition, and the silica gel treated bright stock is used in an amount in the range of 3 to 25 wt. percent.

This invention is particularly applicable to lubricating oil compositions containing added polymeric viscosity index improvers and detergent inhibitors. During experimental work it has been found that when a polymeric viscosity index improver is used in combination with a detergent inhibitor, there appears to be an interaction between the two so as to greatly aggravate the valve underside deposits problem.

Viscosity index improvers are known in the art and are usually used in an amount of 0.5 to 30 wt. percent, preferably 1 to 10 wt. percent, sufiicient to increase the viscosity index of the composition at least 15 units.

This invention is particularly concerned with high quality lubricating oil compositions that are based upon a volatile base stock and contain a polymeric V.I. improver and a detergent inhibitor. Use of the additive of this invention effectively prevents, or at least satisfactor-ily minimizes, the amount of deposits on intake valves.

The polymeric V.I. improver used can be one of several types. High molecular weight (5,000-50,000 Staudinger) hydrocarbon V.I. improvers such as the polymerized lower olefins (i.e. polymerized C C olefins) are quite effective. For example, polymerized butenes, such as polymerized isobutylene having a molecular weight in the range of about 5,000 to 50,000, preferably about 10,000 to 25,000, are quite useful. These polymerized olefins are readily prepared by procedures well known to the art.

Other V.I. improvers include the polymethacrylate esters, fumarate-vinyl acetate copolymers, polyalkyl styrenes, and the like. The viscosity index improver is used in amounts in the range of about 0.5 to 30% by weight, preferably about 1 to 10% by weight, based on the finished lubricating oil. Mixtures of various types of V1. improvers can be used.

Detergent additives can be selected from a large group of materials. They include: metal salts and soaps such as metal naphthenates; zinc soaps of petroleum naphthenic acids, particularly soaps obtained from naphthenic acids having molecular weights of'about 150 to 400; and metal phenates such as the alkali metal, alkaline earth metal and heavy metal phenates. Examples are calcium decyl phenate and barium tert.-octyl phenol..

Specific useful alkyl phenols include the xylenols, thymol, decyl phenols and other long-chain alkyl substituted phenols, wax phenols, petroleum phenols recovered from distillate petroleum oils, and. particularly tertiary aliphatic substituted phenols such as tert. amyl phenol, tert.-octyl phenol and the like can be used. Bis phenols such as 2,2-bis (2-hydroxy-3-tert.-butyl-5-methylphenol)- propane, 2,2 methylene bis (4-methyl-6-tert.-buty1 phenol) and the like can likewise be employed. Various amino phenols and their substituted derivatives such as alkyl para amino phenols and the like can also be used. It is also to be understood that these phenols can be used as such for improving oxidation characteristics. Other suitable detergent additives include metal phosphates and metal phosphites, and high molecular weight polymethacrylate-type esters which can be used as ashless deter gents.

The detergent additives are present in amounts from as low as about 0.5% up to about by weight or even higher, based on total composition, although an amount in the range of about 2 to 8% is generally effective. It is generally preferred that the detergent inhibitor, as in the case of the V.I. improver, contribute very little to O.R.I.

A small amount of a pour depressant additive can also be incorporated in the finished composition in order to obtain improved pour-point stability and decreased pour point. Such pour depressants include condensation products of chlorinated waxy naphthalene or phenol, various polymers and copolymers of unsaturated esters and the like. For example, a copolymer of the fumaric acid esters of coconut oils and of vinyl acetate in a 10:20 weight ratio is an extremely effective pour depressant when used in relatively small concentrations. In the range of about 0.01 to 5% by weight of such materials is usually adequate.

Other additives that can be used in the lubricating oil composition include anti-rust agents such as the partial esters of polyhydroxy compounds including the oleate of sorbitan polyglycol, acid phosphates, and the like; dyes, antioxidants, oiliness agents, assisting agents such as the higher alcohols including octyl alcohol, lauryl alcohol, and stearyl alcohol, extreme pressure agents, etc.

The finished lubricating oil composition can contain one or more of the above types of additives, depending on the extent to which a particular characteristic is to be improved and on the number of characteristics to be improved. It will be realized that some of the above addition agents are multi-functional in that a given addi-- tive can improve more than one characteristic. 5

The finished lubricating composition of this invention meets the inspections set forth in Table III.

TABLE III Viscosity at 210 F., SSU 50 to 75. Viscosity index Above 120. Pour point, F. Below 15. Flash point, F. Above 390. Gravity, API 27 to 33. Tag. Robinson color Above 3. Distillation 10 mm. Hg abs.:

10% point 400-47'5 F. 50% point "500-600 F. 90% point 575-850" F. Conradson carbon, wt. percent Below 0.10. R.I. (resinification index) Below 10 mg./5 gr. Homelite engine underside demerit at hours Less than 2. Octane requirement increase (QBI) Less than 5 units (at EOR above 90).

- Example The following materials were used to obtain the reresults given in this example:

Bright stock A.-This bright stock was obtained from a NorthLouisiana crude. A residual fraction hav ing an initial boiling point of 950 F. was separated by vacuum distillation. This was propane deasphalted to a Conradson carbon content of 2.6 wt. percent at a yield of 42 wt. percent. The deasphalted material was then phenol extracted to a viscosity of 12 6 SSU at 210 F., at a yield of 69 wt. percent. The material was then dewaxed using propane to a pour point of +10 F., at a yield of 74 wt. percent. The bright stock so obtained had a viscosity at 210 F. of 146 SSU, a V1. of 101, a gravity of 26.6 API, and an aromatic content of 30'wt-.

percent. Neurral A.-A distillate havingan SUS vis. of about 40 at 210 F. was obtained by conventional distillation of paraffin-base North Louisiana crudes. This distillate was then extracted with phenol solvent under usual conditions to obtain about a 73% yield of raflinate. The rafiinate was dewaxed using a-conventional methyl ethyl ketone-benzene solvent to obtain approximately 75% yield'of dewaxed'product having a 20 F. pour point.

Neutral B.'A distillate having a Saybolt Universal viscosity (SUS) at 210 F. of about 53 seconds was obtained by conventional distillation of paraflin-base North Louisiana crudes. This distillate was then extracted with phenol solvent under usual conditions to obtain about a 74% yield of rafiinate. The rafiinate was dewaxed using a conventional methyl ethyl ketone-benzene solvent to obtain approximately 75 yield' of dewaxed product having a 15 F. pour point.

Motor Oil A.--This had the following formulation:

Components, vol. percent: Neutral A '80.0 Additives: V

V.I. improver A [13.0

V.I. improver B 1.0

Detergent A 5.0 Zinc dialkyl dithiophosphate (ZDDP) (Lubri- V1. improver A was a polybutene having a molecular weight (Staudinger) of about 1'4,000-15,000. V.I. improver B was a polymethylmethacrylate (Acryloid 747).

Detergent A comprised 37.5% low alkalinity cal cium sulfonate and 62.5% of a P 8 (15 wt. percent) treated neutral barium salt of sulfurized nonyll phenol.

Oil A had the following inspections:

Vis., SUS/ F. 3 61 Vis., SUS/210 F. 68.5 V.I. Percent boiling above 600 F. at 10 mm 0 Motor Oil B.This had the following formulation:

Components, vol. percent:

White oil A.This was an acid treated Coastal dis"- tillate finished to an SUS viscosity at 210 F. of 350.

It meets U.S.P. requirements for white oils and has the following inspections:

Gravity, specific 0.88. Color, Saybolt +30. Viscosity, SUS/ 100 F. 360.

RM. flash, F. .Above 400.

White oil B.-This was an acid treated phenol extracted Coastal distillate finished to a viscosity of about 90 SUS/100 F., and had a P.M. flash above 330 F.

Dimerate A.--This was an ester of a C OX alcohol (2 moles), and dimerized linoleic acid (2 moles).

Dimerate B.This was an ester of a C OX0 alcohol (1 mole), and dimerized linoleic acid (2 moles).

Pelarg0nate.Castor oil esterified with pelargonic acid which is derived from castor oil. (Commercial product sold by Baker Castor Oil Co.)

Silica gel treated bright st0ck.A column, 3" in diameter and 4' high, of commercial silica gel (Davison 28/200 mesh) was prepared. The column was preweted with heptane (500 cc.), and 200 cc. of bright stock A blended with 500 cc. of heptane was then percolated through the column. This was followed by washing with heptane, until pure heptane came through the column. If the aromatic content of the elutriated product was too high, an additional percolation was carried out.

The compositions were made up and tested as indicated by the tables below. The Homelite engine underside demerit test and the laboratory octane requirement test are more fully explained in the terminal portion of the specification.

Table IV shows the eiiect of using synthetic bright stocks in lubricating oil compositions, as evaluated by the Homelite engine test. Table V compares the use of a non-silica gel treated bright stock and the silica gel treated bright stock of this invention. Comparison of Tables IV and V shows that the silica gel treated bright stock is equivalent, if not better than the synthetic bright stocks which synthetics are substantially more expensive. Table V also conclusively shows that the silica gel treated bright stock is superior to the non-treated bright stock and to other highly refined oils, i.e., white oils.

TABLE V Underslde Dernerlt Lubricant 5 Hrs. 20 Hrs.

Motor 011 "A" type made with:

100% Neutral 11" 3.0 3. 0+ 55.9% Neutral A and 30.1% White 011 .4" 1. 5 1.8 100% White Oil 13" 1.8 2. 5 Motor Oil A (Neutral A base) plus:

5% Bright Stock 11"-.- 1.5 3. 3 14% Bright Stock A 2.0 10% Silica gel treated bright stoe 1.0 1. 0 14% Silica gel treated bright stock. 0.5 1.0 Motor Oil B 1. 2 2.0

Table VI shows that the silica gel treated bright stock of this invention does not contribute to O.R.I. Tables V and VI together show that the silica gel treated bright stock is effective in reducing intake valve underside deposits, while not contributing to O.R.I.

TABLE VI Laboratory octane requirement test [1954 Oldsmobile; 9.25/1 Compression Ratio] 1 Corrected for barometer and humidity.

1 Composition adjusted for presence of bright stock.

3 Mechanical failure before equilibrium was established. O.R.I. probably higher at equilibrium.

Table VII gives a comparison of several highly refined bright stocks as used in a lubricating oil composition. A screening evaluation was made using the hydrogen combustion test to determine the resinification index (R.I.). The oils were tested alone and in blend with neutral A. In the same test, neutral A gave a resinification index of 5 mg./5 mg., and motor oil A also gave the same value. This table illustrates that the silica gel treated bright stock is substantially superior as compared to several other types of refined bright stocks. The feed used to prepare the highly refined oils was bright stock A, previously described.

TABLE VII Octane requirement increase PROCESSING BRIGHT STOCK TO REMOVE O.R.I. TENDENCY Process None Phenol Alumina Clay iii/C113, A101 w.lelay A101 w.lc1ay Silica Gel 3 w. e ay Yield, Vol. Percent 100 78 96 98 (est.) (est.) 80 (est.) 70 26. 6 28. 1 27. 7 26. 7 27. 5 26. 7 28. 5 31. 1 2, 209 l, 784 1, 376 2, 068 1, 834 2, 075 1, 126 913 146 133 118 141 133 141 100. 2 94.7 101 105 108 101 103 102 104 114 0. 015 0.004 0. 004 N11 5, Wt. Percent. 0.50 0. 30 0.44 0.41 0.32 0. 43 0.28 0. 03 Conradson Carbon, Wt. Percent 0. 86 0. 58 0. 54 0. 75 0. 52 0. 69 0. 26 0. 01 R.I. 67 C 1. 4768 1.4723 1. 4730 1. 4790 1. 4730 1. 4760 1. 4700 1. 4598 Resingfication Index, mg. 5 (a) (b) (a) (b) (a) (b) (c) (c) (6) (c) (a) (5) Straight. 66. 3, 31 8 63. 3, 44 7 65. 8, 26. 9 29. 5-28. 4 24. 3-25 4 27. 0-20. 5-15. 0 16. 1-26. 0-28. 2 16. 3, 11. 8, 7. 8 5% in Motor Oil 11" 9. 7, 12 4 15.0, 10 4 9. 3, 9.1 6. 9, 7. 8 6. 6-10. 5 10. 6-7. 5 9. 9-7. 5 4. 6, 6. 1

1 Average of two tests. 9 Letters denote tests run at same time. I Represents a triple percolation.

The phenol treated material in column 2 was obtained by extracting bright stock A with 300% anhydrous phenol at 200 F. in a single stage batch treat. The raifinate was stripped of phenol to 78% yield.

T e alumina treated materials were obtained in a conventional manner by percolating bright stock A in heptane solution through Alcoa F-20 alumina at room temperature to a 96% yield.

The clay treated materials of column 4 Were obtained by. contacting bright stock A with Super-filtrol clay at 400-450 F. for one hour. Treat was about lb. clay/ gallon of oil.

The material in column 5 was obtained by contacting bright stock A with 5% r of aluminum chloride for two hours at 250 F., followed by the clay treatment.

'The material of. column 6 was obtained by treatment with 5% aluminum chloride for two hours at 87 F., followed by the clay treatment; and the material in column 7 was obtained by treatment with 5% aluminum chloride for two hours at 350 F., followed by clay treatment.

An attempt was made to obtain a highly acid refined material using sulfuric acid. It was found that a material as' heavy as bright stock A could not be acid treated to'the. same yield level and produce a material even worthy of testing.

The following paragraphsisnmmarize the tests or inspections used in this description.

The viscosities reported were obtained by the standard ASTM methods,-Nos. D-445 and D-88.

The viscosity index (V.I.) provides information as to the change in viscosity of an oil, over the temperature range of 100 to 210 F., and is determined by ASTM D-567.

The Homelite engine intake valve underside deposits test uses a standard engine supplied by the Homelite Company.

The Homelite engine used to evaluate the intake valve deposit forming characteristics of motor lubricants is the driving component of a standard model two cycle gasoline engine-electric generator unit capable of delivering approximately three horsepower or 2200 watts.

The Homelite engine is lubricated by a fuel-oil vapor which reaches all of the critical rubbing metal surfaces in the engine. The fuel and oil are charged directly to the gasoline tank in proportions of pint of oil per gallon of fuel. Fuel and oil are fed to the carburetor, vaporized and then drawn into the engine crankcase on the upward stroke of the piston. On the piston downward stroke, the fuel-oil-air mixture is forced past the piston underside through intake ports in the cylinder wall into the combustion chamber. Compression and ignition occur during the following piston upward stroke.

Due, in part, to the large quantities of lubricating oil vapor throughout the engine, engine deposits build up rapidly during operation. The deposits formed by several lubricants on the hot surface of the piston underside have been found to correlate on a demerit basis with the deposits formed by the same oils on automotive engine intake valve undersides in the field. The similarity of intake conditions is apparent; in the 4 cycle automotive engine, fuel and air flow past a hot, oil-coated intake valve, while in the 2 cycle Homelite engine, fuel, air and oil flow past the hot piston underside. In both cases, deposits resulting primarily from the lubricating oil are formed on hot engine surfaces. This engine test has proved to be a very valuable laboratory test for screening oils prior to full scale road tests.

The test is run for five hours at a speed of approximately 3500 r.p.m. and a load of 2 HP. (115 volts, 13 amps).

The test oil is mixed thoroughly with the test fuel in proportions of pint of oil per gallon of fuel prior to filling the gasoline tank. A record of the fuel used '10 during the test is maintained to obtain a rough check of carburetor performance. ,4 fore and after each test to check the anti-wear characteristics of the test oils. At the conclusion of the test conducted under the above test conditions, the engine is disassembled and the cylinder, piston assembly and crank case are rated'on a demerit basis, on a scale of 0 to 10.

Two methods are used to determine the propensity of an oil to form deposits in the combustion chamber. The first is a combustion test to determine resinification index, which is a useful screening technique for selectingoils for full road tests. It has been found that this combustion test fairly accurately predicts the performance of sample motor oils in actual performance.

This test is described in detail in U.S. Patent 2,761,766, issued September 4, .1956, to Alexander H. Popkin. In this test a known weight of a sample of material to be tested, such as a lubricating oil, a gasoline or other material, is placed in an open vessel having smooth nonabsorptive inner surfaces, such as a glass beaker, porcelain crucible, etc. A hot, smokeless, clean flame, preferably a hydrogen flame, although other clean flame'such as methane, etc. can be used, is directed, into the opening of the vessel. The burner tip, for introducing the gas and air or oxygen (if needed), is directed toward the interior of the vessel. The sample is burned until only a .dry residue, remains. The flame is. discontinued and the vessel is allowed tocool. The total weight of the resinous residue is then determined. When testing oils, the interior of the vessel is wiped carefully, before weighing, with a soft cloth or other soft material to remove carbonaceous deposits but to leave the tenaciously adhering resin-like deposits. The total deposits are weighed when burning fuels. The weight of deposits for a given weight of charge gives the resinification index. Specific testing conditions used for oils, additive-containing oils, additives, and gasolines are shown below:

The octane requirement increase (O.R.I.) test is another method of determining the propensity of motor oils to form combustion chamber deposits. This is a full scale road test. Any car that is critical of gasolines can be used.

For the purposes of this specification, the octane requirement increase is based on any internal combustion engine using gasoline as a fuel, that has a compression ratio above 7 and an equilibrium octane requirement above 70. The composition of this invention has an O.R.I. of less than 10 units for enginm having an E.O.R. in the range of 70 to 90, and less than 5 units for engines having an E.O.R. above 90.

The automobile engine used in Table V1 for the laboratory test was from a 1954 Oldsmobile. A standard gasoline was used. The cycle followed was: idle for 45 seconds; full throttle acceleration to 1675 r.p.m.; 10 minutes at this speed while varying the brake H.P. between 18 and 43; 15 seconds closed throttle motoring at 1400 r.p.m. with ignition, and 30 seconds closed throttle motoring at 1675 r.p.m. with ignition. The air intake temperature was F., the water outlet temperature was F., and the oil sump temperature was 210 F.

Octane requirement was determined by the Standard Uniontown procedure, CRC designation E-1-943, as described in the C.R.C. Handbook, p. 90 et. seq., 1946 edition. Octane requirement increase (O.R.I.) is the difference in the final and initial octane requirement of the engine. Equilibrium octane requirement (E.O.R.)

Piston rings are weighed be 11 is the octane requirement of the engine after several thousand equivalent miles (about 12,000 miles or about 295 hours of operation in this case) of use, at which octane requirement reaches a substantially constant level. O.R.I. and E.O.R. are based on road octane numbers using primary reference fuels.

Having described this invention, what is sought to be protected by Letters Patent is succinctly set forth in the following claims.

What is claimed is:

1. A lubricating oil composition for internal combustion engines inhibited against: the formation of intake valve underside deposits and engine octane requirement increase, said composition having a viscosity of 50 to 70 SSU at 210 F., a viscosity index above 120 and comprising: a major amount of a volatile mineral oil base stock having an end boiling point below 600 F., at a pressure of 10 millimeters Hg absolute; about 1 to 10 wt. percent of a viscosity index improver selected from the group consisting of polymers of C to C monoolefins and polymeric materials prepared by polymerizing unsaturated esters of carboxylic acid; about .5 to wt. percent of a detergent inhibitor additive selected from the group consisting of metal salts of sulfonic acid, metal salts of alkyl phenols and P 5 treated metal salts of sulfurized alkyl phenols; wherein said combination of said base stock with said V1. and said deter-gent additive normally forms intake valve underside deposits in internal combustion engines, and as an inhibitor of said deposits about 3 to 25 wt. percent of a deasphalted, dewaxed, silica gel treated mineral oil virgin bright stock having a viscosity index between 100 and 120, a viscosity at 210 F. in the range of 70 to 150 SSU, containing less than 5 wt. percent of single ring aromatics,

12 substantially free of condensed ring aromatics, having a sulfur content of 0 to .05 wt. percent and an initial boiling point above 850 F.

2. A lubricating oil composition according to claim 1 wherein said V.I. improver is a mixture of polybutene and a polymethylmethacrylate, and said detergent is a mixture of calcium sulfonate and a phosphosulfurized treated neutral barium salt of sulfurized nonyl phenol.

3. A lubricating oil composition according to claim 1 comprising about volume percent of said volatile mineral oil base stock, about 13 volume percent of a polybutene viscosity index improver having a Staudinger molecular weight of about 14,000 to 15,000, about 1 volume percent of polymethylmethacrylate, about 5 volume percent of a detergent inhibitor additive mixture consisting of 37.5 percent calcium sulfonate and 62.5 percent of a P 8 treated neutral barium salt of sulfurized nonyl phenol, and about 14 volume percent of said deasphalted, dewaxed silica gel treated mineral oil virgin bright stock.

References Cited in the file of this patent UNITED STATES PATENTS 2,336,195 Sparks et al. Dec. 7, 1943 2,585,490 Olsen Feb. 12, 1952 2,589,981 Weeks Mar. 18, 1952 2,779,317 Holder et al. Ian. 29, 1957 2,849,398 Moody et al. Aug. 26, 1958 OTHER REFERENCES Petroleum Refining With Chemicals (Kalichevsky et a1), pub. by Elsevier, N.Y., 1956, pages 201203.

Motor Oils and Engine Lubrication (Georgi), publ.

by Reinhold Publ. Corp., N.Y., 1950, page 108. 

1. A LUBRICATING OIL COMPOSITION FOR INTERNAL COMBUSTION ENGINES INHIBITED AGAINST: THE FORMATION OF INTAKE VALVE, UNDERSIDE DEPOSITS AND ENGINE OCTANE REQUIREMENT INCREASE, SAID COMPOSITION HAVING A VISCOSITY OF 50 TO 70 SSU AT 210*F., A VISCOSITY INDEX ABOVE 120 AND COMPRISING: A MAJOR AMOUNT OF A VOLATILE MINERAL OIL BASE STOCK HAVING AN END BOILING POINT BELOW 600*F., AT A PRESSURE OF 10 MILLIMETERS HG ABSOLUTE, ABOUT 1 TO 10WT. PERCENT OF A VISCOSITY INDEX IMPROVER SELECTED FROM THE GROUP CONSISTING OF POLYMERS OF C3 TO C5 MONOOLEFINS AND POLYMERIC MATERIALS PREPARED BY POLYMERIZING UNSATURATED ESTERS OF CARBOXYLIC ACID, ABOUT .5 TO 10 WT. PERCENT OF A DETERGENT INHIBITOR ADDITIVE SELECTED FROM THE GROUP CONSISTING OF METAL SALTS OF SULFONIC ACID, METAL SALTS OF ALKYL PHENOLS AND P2S5 TREATED METAL SALTS OF SULFURIZED ALKYL PHENOLS, WHEREIN SAID COMBINATION OF SAID BASE STOCK WITH SAID V.I. AND SAID DETERGENT ADDITIVE NORMALLY FORMS INTAKE VALVE UNDERSIDE DEPOSITS IN INTERNAL COMBUSTION ENGINES, AND AS AN INHIBITOR OF SAID DEPOSITS ABOUT 3 TO 25 WT. PERCENT OF A DEASPHALTED, DEWAXED, SILICA GEL TREATED MINERAL OIL VIRGIN BRIGHT STOCK HAVING A VISCOSITY INDEX BETWEEN 100 AND 120, A VISCOSITY AT 210*F. IN THE RANGE OF 70 TO 150 SSU, CONTAINING LESS THAN 5 WT. PERCENT OF SINGLE RING AROMATICS, SUBSTANTIALLY FREE OF CONDENSED RING AROMATICS, HAVING A SULFUR CONTENT OF 0 TO .05 WT. PERCENT AND AN INITIAL BOILING POINT ABOVE 850*F. 